Lightweight hydraulically fired minesweeping cutter

ABSTRACT

A minesweeping cutter device includes a tubular body closed at one end andaving a cable engaging recess at the other end, a barrel member reciprocable in the body by cable engagement to fire a chisel propelling charge. The chisel has its cutting edge spaced from the cable until the charge is fired so that a reliable cutting velocity is achieved before impact. An erecting vane has a sweep wire channel and is provided with a sliding gate on a guide rail that diverges angularly from the axis of the channel.

BACKGROUND OF THE INVENTION

This invention relates to the field of minesweeping, and moreparticularly to an improved cutter device for severing mine mooringcables engaged by a sweep wire.

It has been the practice to provide the sweep wire of towed minesweepinggear with one or more explosively actuated cutters for severing the minemooring cables. The cutters typically comprise a body mounted on thesweep wire and having a jaw or hook which is engaged by a mooring cableas it slides along the towed sweep wire. The body is usually providedwith a vane that assumes a horizontal position aft of the sweep wireduring tow and positions the body with the jaw or hook ready to beengaged by a mooring cable. Upon such engagement a firing sequence isinitiated to propel a chisel through the cable to sever it, usuallyagainst an anvil.

U.S. Pat. No. 2,422,506 provides an example of a minesweeping cutterwherein the firing mechanism is a spring and lever apparatus and thecable is backed by an anvil during cutting. U.S. Pat. No. 3,760,674utilizes a spring driven plunger and hydraulic column means in thefiring mechanism, and an anvil. U.S. Pat. No. 4,074,650 discloses afiring mechanism wherein the chisel is engaged by the mooring cable anddisplaced with its barrel to shear a pin and allow a spring to drive thebarrel rearwardly so that a confined slug of seawater causes a pistoncarried firing pin to actuate an explosive cartridge. In that device thechisel is intended to be driven through the mooring cable withoutbenefit of backing by an anvil, or the like. While the lack of an anvilis desirable from the standpoint of cost and simplicity, theconfiguration taught in the mentioned patent has the shortcoming of notdeveloping an impact velocity in the chisel before contact with thecable, and hence is limited in severing capability.

The use of springs, levers, and the like, in the firing mechanism notonly reduces reliability and adds to initial cost, but also increasesthe time and effort that must be expended in disassembly, cleaning,lubricating and reassembly after streaming. Moreover, existing cutterdevices incorporate complex means of attachment to the sweep wire, oftenrequiring the use of both hands, thereby adding to personnel risk inheavy weather.

SUMMARY OF THE INVENTION

With the foregoing in mind, it is a principal object of this inventionto provide an improved, lightweight, minesweeping cable cutter.

Another object is to provide a cable cutter that avoids use of springs,levers, and the like in the firing mechanism.

Yet another object is to provide a mine mooring cable cutter that islightweight, relatively inexpensive, and easy to attach to or removefrom a sweep wire.

As another important object, the invention aims to provide a simplifiedand yet more effectual mine cable cutter of the type wherein the chiselsevers the mooring cable without use of an anvil.

Other objects and many of the attendant advantages will be reallyappreciated as the subject invention becomes better understood byreference to the following detailed description, when considered inconjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a minesweeping cutter embodying the invention;

FIG. 2 is a fragmentary longitudinal sectional view of the cutter ofFIG. 1;

FIG. 3 is a sectional view taken substantially along line 3--3 of FIG.1; and

FIG. 4 is a sectional view taken substantially along line 4--4 of FIG.1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the exemplary form of the invention illustrated in the drawings anddescribed hereinafter, and with reference first to FIG. 1, aminesweeping cutter 10 is adapted to be streamed on a sweep wire 12 asone of a plurality of such cutters, spaced therealong by stops 12a, forthe purpose of severing mine mooring cables such as a cable 14. Thedevice 10 comprises a generally cylindrical cutter body 16 having oneend formed to define a V-shaped recess 18. Mounted on the body 16 is avane 20 which lies in a horizontal plane during tow and serves toposition the body 16 with the recess 18 oriented to receive a verticalmooring cable 14 which is engaged by the sweep wire 12 and slidestherealong into the recess.

Referring now to FIG. 2, it will be seen that the body 16 comprises atubular wall portion 16a defining a lumen or bore 22 that is open at theend having recess 18, and an end wall 16b closing the bore 22 at theopposite end. The body 16 is advantageously made of stainless steel orother high strength, corrosion resistant material. Disposed in bore 22of body 16 is a barrel 26, conveniently formed of a rigid, dimensionallystable plastic material such as nylon, "DELRIN," or the like. Barrel 26has a nice sliding fit within bore 22 and is formed to define first andsecond, axially aligned cylindrical bores 28 and 30 separated by a wall32 and pierceable metal diaphragm or disc 32a. Bore 28, which opens inthe jaw or recess 18 at the open end of body 16, carries an explosivelydriven cutting chisel 34. The chisel 34 is normally restrained againstmovement in bore 28, and the barrel 26 is normally restrained againstmovement in bore 22, by a shear pin or screw 36 extending through wall16a, through the wall of barrel 34 and into chisel 34. Loaded in barrel34 behind the chisel 34 is an explosive cartridge 36 surrounded by aspacer ring 40.

Disposed in the bore 30 of barrel 26 is a piston 42 carrying an axialfiring pin 44 adapted to be driven by piston 42 through metal diaphragmor disc 32a and an aperture 46 in wall 32 into a percussion primer ofcartridge 38. Barrel 26 and piston 42, together with body 16 define achamber 48 that is adapted to be flooded by seawater through holes 50 inwall 16a during towing. Similarly, the space between piston 42 and disc32a is flooded via holes 52. A pin 54 is conveniently inserted in one ofthe openings 52 to preclude any possibility of the piston 42 and firingpin 44 inadvertently moving and firing the device. The pin 54 iswithdrawn just prior to streaming.

The body 16 and vane 20 are secured together by screws 56, the ends ofwhich project into an axial groove 58 in the surface of barrel 26. Thegroove and screw ends cooperate to maintain the barrel in a rotativeposition such that the cutting edge 34a of the chisel 34 is transverseto the mooring cable receiving jaw or recess 18 and to a mooring cablewhen engaged therein.

It is important to note that the forward end portion of the barrel 26 isexposed in recess 18 and that a portion of the barrel extends beyond thecutting edge 34a of the chisel by a distance d. This distance, as willbecome more apparent in the description of the operation, is necessaryto reliable operation of the cutter.

The erecting fin or vane 20 is preferably formed of a suitable rigidplastic material and is configured to cooperate with an easily operatedgate member 60 for use in attaching the cutter to or removing it fromthe sweep wire 12. Gate member 60 is generally triangular in shape andis slidably movable between its closed or full line position and an openor dot and dash line position. Referring additionally to FIG. 3, the fin20 defines a channel 62 in which the sweep wire 12 is confined by theclosed gate 60. The gate is slidably mounted on a guide rail 64 andbecause of the angle of divergence of the rail 64 from the axis of thechannel 62, movement of the gate toward its dot and dash position ofFIG. 1 creates an opening between the gate edge 66 and the edge 68 ofthe channel through which the sweep wire can pass.

The gate 60 is provided with a latch for releasably securing the gate inits closed position. To this end, a flat or reed spring detent 70 hasone end fixed at 72 to the fin 20, as is best shown in FIG. 4, and hasits free end engagable in a recess 74 of the gate 60. A push-button 76is carried in the gate 60 and is operable to depress the spring detent70 to disengage its free end from the recess 74 to release the gate forsliding movement to its open position, in which position the free end ofthe spring detent engages a second recess to prevent further movement ofthe gate in the opening direction. Upon return of the gate to its closedposition, the spring detent automatically latches it. A small hole 76 isprovided in gate 60 for insertion of a probe to depress the detent andallow disassembly of the gate from the fin. The device 10, with its gateopen, is readily hung on a sweep wire 12 with one hand, and the gatethen closed by simply striking it toward its closed position.

MODE OF OPERATION

A mine mooring cable 14, engaged in recess 18 during a sweep operation,presses with increasing force against the exposed end portion of barrel26 until the shear screw 36 suddenly yields between wall 16a and thebarrel allowing the barrel, chisel 34, and piston 42 to abruptly moverearwardly in unison toward end wall 16b until holes 50 are covered bythe barrel. Thereafter, rearward movement of barrel 26 causes water inchamber 48 to move piston 42 forward relative to the barrel so thatfiring pin 44 is rapidly driven through disc 32a into the primer ofexplosive cartridge 38. The cartridge is thereby detonated and buildspressure behind the chisel 34 until the screw shears between the chiseland the barrel allowing the chisel to be abruptly driven forward in thebarrel with great acceleration. The earlier mentioned distance d that istraveled by the chisel before impact with the cable 14 permits thechisel to attain such a velocity that the cable 14 is readily severedeven without backup, as by an anvil.

The screws 56 securing the body 16 to the fin 20 and the strength of theplastic section through which they extend are so selected that thereactive kick-back or recoil of the body upon discharge of the chiselcauses the body to rip free from the vane 20. Accordingly, having oncebeen discharged or fired, the body 16 of the cutter device 10 is nolonger present on the sweep wire and a subsequent mooring cable will beengaged and cut by the next cutter device on the sweep cable.

Obviously, other embodiments and modifications of the subject inventionwill readily come to the mind of one skilled in the art having thebenefit of the teachings presented in the foregoing description and thedrawing. It is, therefore, to be understood that this invention is notto be limited thereto and that said modifications and embodiments areintended to be included within the scope of the appended claims.

What is claimed is:
 1. A mine mooring cable cutter device for use on asweep wire, said device comprising:a tubular metal cutter body defininga lumen closed at one end of the body and opening in a V-shaped recessat the other end that is engageable by a mooring cable; an erecting vaneformed of plastic material attached to and extending laterally from saidbody for holding said body in a predetermined attitude, said erectingvane comprising a vane element defining therein a longitudinal channeladapted to receive a sweep wire, a guide rail formed in said vane andhaving an angle of divergence relative to said channel, a generallytriangular gate member slidably mounted on said guide rail for slidingmovement therealong between open and closed positions relative to saidchannel, and latch means for releasably holding said gate member in saidclosed position; a plastic barrel member carried in said body lumen andhaving an outer end portion exposed in said recess for engagement andmovement by a mooring cable, said barrel member having an axial bore insaid outer end portion; a chisel disposed in said axial bore of saidbarrel member and having a cutting edge disposed a predetermineddistance within said end portion; explosive charge means disposed insaid axial bore for propelling said chisel; said barrel member beingreleasably held against movement relative to said body by a shearelement so as to shear said element and move abruptly upon apredetermined force exerted on said barrel member by a mine mooringcable; said chisel being releasably held against movement relative tosaid barrel member by a shear element so as to shear said element andmove abruptly upon a predetermined force exerted on said chisel by saidexplosive charge, said barrel member having another axial bore in itsinner end portion separated from the first mentioned axial bore by wallmeans; a piston disposed in said other axial bore of said barrel member;a firing pin mounted on said piston; said barrel member, said piston andsaid closed end of said body defining a chamber; an opening through saidbody member into said lumen for flooding said chamber with water priorto firing, said opening being closed by said barrel member upon saidmovement relative to said body so that water in said chamber acts onsaid piston to drive said firing pin through said wall means to firesaid explosive charge solely by the force of said mooring cable actingagainst said barrel member, whereby said chisel is accelerated throughsaid predetermined distance before impacting and severing said mooringcable without backing of said cable by anvil means.
 2. A cutter deviceas defined in claim 1, and wherein:said barrel member is releasably heldagainst movement relative to said body by a shear element so as to shearsaid element and move abruptly upon a predetermined force exerted onsaid barrel member by a mine mooring cable; and said chisel isreleasably held against movement relative to said barrel member by ashear element so as to shear said element and move abruptly upon apredetermined force exerted on said chisel by said explosive charge. 3.A cutter device as defined in claim 1, and wherein said erecting vanecomprising:a vane element defining a longitudinal channel adapted toreceive a sweep wire; a gate member slidably mounted on said vaneelement for movement in directions angularly divergent to saidlongitudinal channel between open and closed positions; and latch meansfor releasably holding said gate member in said closed position.
 4. Acutter device as defined in claim 3, and wherein:said body comprises abore closed at one end and opening at the other end in said cableengaging recess; said barrel member being mounted in said bore of saidbody and having another axial bore in its inner end portion andseparated the first mentioned axial bore by wall means; a pistondisposed in said other axial bore of said barrel member; a firing pinmounted on said piston; said barrel member, said piston and said closedend of said body defining a chamber; passage means for flooding saidchamber with water prior to firing, said passage means being closed bysaid movement of said barrel member relative to said body; whereby waterin said chamber acts on said piston to drive said firing pin throughsaid wall means to fire said explosive charge solely by the force ofsaid mooring cable acting against said barrel member.